Control method for enhancing driving capacity of vehicle on ice and snow or non-paved road surface

Abstract

The invention discloses a control method for enhancing the driving capacity of a vehicle on an ice and snow or non-paved road surface. The control method comprises the following steps: S1, identifying road surface information on which the vehicle runs; s2, starting a control mode; s3, triggering the control mode; s4, the automobile is controlled to enter a stable crawling mode, the feedforward basic torque of automobile running is calculated and adjusted, the feedback adjusting torque is obtained, and finally the comprehensive torque is obtained; s5, judging whether the automobile is in a stable driving state or not; s6, the automobile is controlled to enter a stable acceleration mode, and the comprehensive torque is gradually increased; and S7, when the driving wheels do not have the unstable state, arbitrating the increased comprehensive torque obtained in the step S6 and the torque generated when the driver steps on the accelerator, and taking the minimum value of the two as the final target torque to drive the automobile to leave the current road surface. According to the control method, control can be started when the wheels do not slip, so that the automobile can stably start and break away from a severe road surface.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads. Background Art

[0002] In winter, rainy and snowy weather will cause snow or even ice on the road, or on unpaved gravel and other roads, especially when the road has a certain slope, the grip provided by the road surface will be greatly reduced. Drivers must be very careful when driving on such roads. If the accelerator is pressed a little harder, it may cause the wheels to slip quickly, which is very dangerous.

[0003] Traditional traction control systems can only trigger control when wheel slippage is detected, that is, when the wheel has a large slip rate. In addition, the driving ability of cars is getting stronger and stronger, especially electric cars, which have a large peak torque at low speed and a large torque loading slope. On roads with poor adhesion such as ice, snow, sand and gravel, even if the traditional traction control system starts to control, it is difficult to avoid a large slip rate on the wheels. At this time, the vehicle is prone to lateral movement or tail swinging. Moreover, if the road is on a slope, the vehicle may slide backward, which is very dangerous. In addition, wheel slippage will damage the road surface under the current wheel, and the decrease in road adhesion will continue to increase the difficulty of starting or getting out of trouble. Summary of the invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide a control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads. The control method can start control before the wheels slip, so that the vehicle can start stably and get off the bad road.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads, comprising:

[0007] S1, identifying the road surface information on which the car is traveling;

[0008] S2, if the road surface information is ice or snow or unpaved road, start the control mode;

[0009] S3, determining whether the driver's throttle request meets the control mode triggering requirement;

[0010] S4, if step S3 is met, the vehicle is controlled to enter a stable crawling mode, in which a feedforward basic torque for the vehicle is calculated according to the current vehicle mass, wheel rolling radius, road slope, and road type, and the feedforward basic torque is adjusted according to actual vehicle operating parameters to obtain a feedback adjustment torque, and a comprehensive torque is obtained according to the feedforward basic torque and the feedback adjustment torque;

[0011] S5, determining whether the vehicle is in a stable driving state;

[0012] S6, if the vehicle is in a stable driving state, controlling the vehicle to enter a stable acceleration mode, in which the comprehensive torque is gradually increased;

[0013] S7, determine whether the driving wheel is in an unstable state. If the driving wheel is in an unstable state, return to step S4; if the driving wheel is not in an unstable state, arbitrate the increased comprehensive torque obtained in step S6 and the torque generated by the driver stepping on the accelerator, and take the minimum value of the two as the final target torque to drive the car off the current road surface.

[0014] In some embodiments, in step S3, the control mode is triggered if any of the following conditions is met:

[0015] The throttle opening and change speed are greater than the set value;

[0016] The rotation acceleration of the driving wheel is greater than the set value;

[0017] The jerk of the drive wheel is greater than the set value.

[0018] In some embodiments, in step S4, the feedforward basic torque T veh The calculation formula is:

[0019] T veh =m veh *a cor *r whl +T offset ;

[0020] Among them, m veh is the mass of the car; a cor is the comprehensive target acceleration; r whl Rolling radius of the wheel; T offset is the torque compensation value, which can be obtained through calibration;

[0021] The comprehensive target acceleration a cor Calculated by the following formula:

[0022] a cor =max(a slope , a mue )

[0023] Among them, a slope is the target acceleration converted from the road slope; a mue is the target acceleration converted from the road surface type.

[0024] In some embodiments, a mue The calculation method is as follows:

[0025] a mue =mue*g;

[0026] mue=c*mue1+(1-c)*mue2;

[0027] Wherein, c is the weighting coefficient, 0≤c≤1; mue1 is the road adhesion coefficient obtained from the road type information; mue2 is the road adhesion coefficient obtained by estimation;

[0028]

[0029]

[0030] F Road =F drv -F brk -F int ;

[0031] F int =I*α / r whl ;

[0032] Where, α is the rotational acceleration of the wheel; I is the moment of inertia of the wheel; F int is the wheel rotation inertia force; F brk is the wheel braking force; F drv is the wheel driving force; F Road is the road reaction force; a y is the lateral acceleration of the wheel; g is the acceleration due to gravity; mue long is the road adhesion coefficient in the longitudinal direction of the vehicle coordinate system; mue lat is the road adhesion coefficient in the lateral direction of the vehicle coordinate system.

[0033] In some embodiments, the method for obtaining the feedback adjustment torque in step S4 is:

[0034] S41, setting target parameter values ​​of vehicle operation parameters;

[0035] S42, testing actual operating parameter values ​​of the vehicle under the feedforward basic torque drive;

[0036] S43, calculating the difference between the target parameter value and the actual operating parameter value;

[0037] S44, adjusting the feedforward basic torque through an algorithm according to the difference to obtain the feedback adjustment torque.

[0038] In some embodiments, the vehicle operating parameter for adjusting the feedforward basic torque in step S4 is one or more of the rotation speed of the driving wheel, the rotation acceleration of the driving wheel and the jerk of the driving wheel.

[0039] In some embodiments, in step S4, when the automobile is a four-wheel drive vehicle, after obtaining the comprehensive torque, the comprehensive torque is distributed to the drive systems of the front axle and the rear axle according to the real-time dynamic loads of the front axle and the rear axle of the automobile for execution.

[0040] In some embodiments, in step S5, whether the vehicle is in a stable driving state is determined by the rotational acceleration or jerk of the driving wheel; when the changes in the rotational acceleration or jerk of the driving wheel do not exceed the set value within a set time range, the vehicle is determined to be in a stable driving state.

[0041] In some embodiments, in step S6, in a stable acceleration mode, the comprehensive torque is gradually increased at a constant rate of change per unit time.

[0042] In some embodiments, when the automobile increases the comprehensive torque to a four-wheel drive vehicle, the rate of change of the front axle per unit time is greater than the rate of change of the rear axle per unit time.

[0043] In some embodiments, in step S7, whether the driving wheel is in an unstable state is determined by the rotational acceleration or jerk of the driving wheel; when the rotational acceleration or jerk of the driving wheel is greater than a set value, it is determined that the driving wheel is in an unstable state.

[0044] Due to the application of the above technical solution, the control method of the present invention for enhancing the driving ability of a vehicle on ice, snow or unpaved roads has the following advantages compared with the prior art:

[0045] (1) Different feedforward basic torques can be obtained according to different road surface information, ensuring that the vehicle can obtain appropriate driving force on different types of road surfaces;

[0046] (2) When the driver steps on the accelerator, predictive control can be performed based on the accelerator request, ensuring that control begins before the wheels slip. By using the principle that the tire rolling friction limit is greater than the sliding friction limit, the tire adhesion limit is fully utilized when the car is getting out of trouble on a harsh road environment.

[0047] (3) Control is initiated before the wheels begin to slip, which can also prevent wheel slip from damaging the current road surface, especially on snowy or gravel roads. Wheel slip will make the road environment worse and more difficult to escape;

[0048] (4) The vehicle can be controlled to enter a stable crawling mode and a stable acceleration mode. The stable crawling mode ensures that the vehicle can smoothly leave the current road surface, and the stable acceleration mode ensures that the vehicle has a certain driving ability after leaving the road surface. This can balance the vehicle's need to escape from trouble, stability during driving, and power.

[0049] (5) The comprehensive torque of the vehicle is obtained through the feedforward basic torque and the feedback adjustment torque, and the torque can be limited according to the dynamics of the drive wheels, ensuring the vehicle's ability to get out of trouble and avoiding the drive wheels from being in an unsteady state. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Attached Figure 1 A schematic diagram showing the relationship between the friction between the wheels and the road surface and the driving force of the vehicle;

[0051] Attached Figure 2 This is a flow chart of the control method of this embodiment for enhancing the driving ability of a vehicle on ice, snow or unpaved roads. DETAILED DESCRIPTION

[0052] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] The relationship between the friction between the wheels and the road and the driving force of the car is as follows Figure 1 As shown in FIG. 1 , the maximum friction force occurs when the relative movement between the wheel and the road surface is very small. Therefore, in the present invention, control is started before the wheel slips. The flow chart of the control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads of the present invention is shown in FIG. Figure 2 As shown, the specific steps include:

[0054] S1, identifying the road surface information on which the car is traveling.

[0055] The road surface information can be identified by the driver. For an automatic driving or assisted driving system, the road surface information can be identified by a camera or other means.

[0056] S2, start control mode.

[0057] If the road surface information on which the car is traveling is determined to be ice, snow or unpaved, the control mode is activated. The control mode can be activated by physical or car central control soft switch. The road surface mode selection switch on the car can also be used. When the road surface mode is switched to ice, snow, sand, mud and other modes, the control mode is considered to be activated. Or for automatic driving or assisted driving systems, when the camera or other methods identify poor road surfaces such as ice, snow, sand, mud, etc., the control mode is considered to be activated. The control mode activation methods include but are not limited to the above methods.

[0058] S3, determining whether the driver's throttle request meets the control mode triggering requirement.

[0059] When the driver steps on the accelerator deeply and any of the following conditions are met, the control mode is triggered:

[0060] The throttle opening and change speed are greater than the set value. For example, the throttle opening is greater than 30%, and the change speed is greater than 400% / s.

[0061] The rotation acceleration of the driving wheel is greater than the set value. For example, the rotation acceleration of the driving wheel is greater than 10m / s 2 .

[0062] The jerk of the driving wheel is greater than the set value. For example, the jerk of the driving wheel is greater than 50m / s 3 .

[0063] S4, stable crawling mode.

[0064] (1) Calculate the feedforward base torque.

[0065] When the control mode is triggered, the vehicle first enters the stable creeping mode, in which the feedforward basic torque for the vehicle is calculated based on the current vehicle mass, wheel rolling radius, road slope, and road type.

[0066] Feedforward base torque T veh The calculation formula is:

[0067] T veh =m veh *a cor *r whl +T offset .

[0068] Among them, m veh is the mass of the car; a cor is the comprehensive target acceleration; r whl Rolling radius of the wheel; T offset is the torque compensation value, which can be obtained through calibration.

[0069] In the above formula, the comprehensive target acceleration a cor Calculated by the following formula:

[0070] a cor =max(a slope , a mue ).

[0071] Among them, a slope is the target acceleration converted from the road slope; a mue is the target acceleration converted from the road surface type.

[0072] a mue The calculation method is as follows:

[0073] a mue =mue*g;

[0074] mue=c*mue1+(1-c)*mue2;

[0075] Wherein, c is the weighting coefficient, 0≤c≤1; mue1 is the road adhesion coefficient obtained from the road type information; and mue2 is the road adhesion coefficient obtained by estimation.

[0076] The calculation method of mue2 is as follows:

[0077]

[0078] F Road =F drv -F brk -F int ;

[0079] F int =I*α / r whl ;

[0080] Among them, r whl is the rolling radius of the wheel; α is the rotational acceleration of the wheel; I is the moment of inertia of the wheel; F int is the wheel rotation inertia force; F brk is the wheel braking force; F drv is the wheel driving force; F Road is the road reaction force; m veh is the mass of the car; a y is the lateral acceleration of the wheel; g is the acceleration due to gravity; mue long is the road adhesion coefficient in the longitudinal direction of the vehicle coordinate system; mue lat is the road adhesion coefficient in the lateral direction of the vehicle coordinate system.

[0081] After the feedforward base torque is obtained, the vehicle is driven by the feedforward base torque.

[0082] (2) Calculate the feedback adjustment torque.

[0083] The feedforward basic torque is adjusted according to the actual operating parameters of the vehicle to obtain the feedback adjustment torque. The specific steps include:

[0084] S41, setting a target parameter value of a vehicle operation parameter. The vehicle operation parameter is specifically one or more of a rotation speed of a driving wheel, a rotation acceleration of a driving wheel, and a jerk of a driving wheel.

[0085] S42, testing the actual operating parameter values ​​of the vehicle under the feedforward basic torque drive.

[0086] S43, calculating the difference between the target parameter value and the actual operating parameter value.

[0087] S44, adjusting the feedforward basic torque by an algorithm according to the difference to obtain the feedback adjustment torque. The algorithm mentioned here can be a PID algorithm, and of course other algorithms can also be used.

[0088] (3) Calculate the comprehensive torque.

[0089] The comprehensive torque is obtained based on the feedforward basic torque and the feedback adjustment torque, and the vehicle is driven on the current road surface by the comprehensive torque.

[0090] (4) Torque distribution.

[0091] When the vehicle is a four-wheel drive vehicle, after obtaining the comprehensive torque, the comprehensive torque is distributed to the drive systems of the front axle and the rear axle according to the real-time dynamic loads of the front axle and the rear axle of the vehicle. The real-time dynamic loads of the front axle and the rear axle of the vehicle during driving can be calculated according to the methods in the prior art.

[0092] S5, determining whether the vehicle is in a stable driving state.

[0093] The rotation acceleration or jerk of the driving wheel is used to determine whether the vehicle is in a stable driving state. If the change in the rotation acceleration or jerk of the driving wheel does not exceed the set value within the set time range, the vehicle is determined to be in a stable driving state.

[0094] S6, stable acceleration mode.

[0095] When the vehicle is in a stable driving state, the vehicle is controlled to enter a stable acceleration mode. In this mode, the comprehensive torque is gradually increased, and the specific increase method is to gradually increase the comprehensive torque at a constant change rate per unit time. In this embodiment, the comprehensive torque is gradually increased at a change rate of 200Nm / s.

[0096] When the comprehensive torque is increased for a four-wheel drive vehicle, the rate of change of the front axle per unit time is greater than the rate of change of the rear axle per unit time. This can avoid the problem that the rear axle slips first when the vehicle slips, thereby affecting the stability of the vehicle. The arrangement of the present invention can take into account both the acceleration capability and stability of the vehicle.

[0097] S7, determining whether the driving wheel is in an unstable state.

[0098] If the driving wheel is in an unstable state, return to step S4. Specifically, the driving wheel is judged to be in an unstable state by the rotation acceleration or jerk of the driving wheel. When the rotation acceleration or jerk of the driving wheel is greater than a set value, it is judged that the driving wheel is in an unstable state.

[0099] If the driving wheel is not in an unstable state, the increased comprehensive torque obtained in step S6 and the torque generated by the driver stepping on the accelerator are arbitrated, and the minimum value of the two is taken as the final target torque to drive the car off the current road surface.

[0100] During the operation of the above two modes, if the driver turns off the function switch or the wheel speed sensor of the vehicle is damaged, the control mode will be automatically turned off.

[0101] In summary, the control method of the present invention has the following advantages:

[0102] (1) A road mode selection switch on the vehicle can be used to set different feedforward basic torques when switching road modes, thereby ensuring that the vehicle can obtain appropriate driving force on different types of road surfaces.

[0103] (2) When the automatic driving or assisted driving system identifies a poor road surface such as ice, snow, sand, mud, etc. through a camera or other means, the control mode is considered to be on. When the road mode is switched, different feedforward basic torques can be set to ensure that the vehicle can obtain appropriate driving force on different types of road surfaces.

[0104] (3) Predictive control is performed based on information such as the driver's throttle opening, throttle opening change rate, drive wheel rotation acceleration, and drive wheel jerk. The control mode is automatically activated to ensure that control is initiated before the wheels slip. The principle that the tire's rolling friction limit is greater than its sliding friction limit is used to ensure that the tire's adhesion limit is fully utilized when the vehicle is trying to escape from a bad road environment.

[0105] (4) Control is initiated before the wheels begin to slip, which can also prevent wheel slip from damaging the current road surface, especially on snowy or gravel roads. Wheel slip will make the road environment worse and more difficult to escape.

[0106] (5) The control mode is divided into two modes: stable creeping mode and stable acceleration mode. The stable creeping mode ensures that the car can smoothly leave the current road surface, and the stable acceleration mode ensures that the car has a certain driving ability after leaving the road surface, which can balance the car's escape needs, stability and power during driving.

[0107] (6) The calculation of the vehicle's required torque is divided into feedforward basic torque calculation and feedback adjustment torque calculation, and the torque is limited according to the dynamics of the drive wheels to ensure the vehicle's ability to escape from difficulties while avoiding the drive wheels from being in an unsteady state.

[0108] (7) If the vehicle is a four-wheel drive vehicle, the front and rear axles can be set with different comprehensive torque growth change rates, for example, a larger change rate is used for the front axle and a smaller change rate is used for the rear axle, so as to take into account both the vehicle's acceleration capability and stability.

[0109] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads, characterized in that: include: S1, identifying the road surface information on which the car is traveling; S2, if the road surface information is ice or snow or unpaved road, start the control mode; S3, determining whether the driver's throttle request meets the control mode triggering requirement; S4, if step S3 is met, the vehicle is controlled to enter a stable crawling mode, in which a feedforward basic torque for the vehicle is calculated according to the current vehicle mass, wheel rolling radius, road slope, and road type, and the feedforward basic torque is adjusted according to actual vehicle operating parameters to obtain a feedback adjustment torque, and a comprehensive torque is obtained according to the feedforward basic torque and the feedback adjustment torque; S5, determining whether the vehicle is in a stable driving state; S6, if the vehicle is in a stable driving state, controlling the vehicle to enter a stable acceleration mode, in which the comprehensive torque is gradually increased; S7, determine whether the driving wheel is in an unstable state. If the driving wheel is in an unstable state, return to step S4; if the driving wheel is not in an unstable state, arbitrate the increased comprehensive torque obtained in step S6 and the torque generated by the driver stepping on the accelerator, and take the minimum value of the two as the final target torque to drive the car off the current road surface.

2. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: In step S3, the control mode is triggered if any of the following conditions is met: The throttle opening and change speed are greater than the set value; The rotation acceleration of the driving wheel is greater than the set value; The jerk of the drive wheel is greater than the set value.

3. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: In step S4, the feedforward basic torque T veh The calculation formula is: T veh =m veh *a cor *r whl +T offset ; Among them, m veh is the mass of the car; a cor is the comprehensive target acceleration; r whl Rolling radius of the wheel; T offset is the torque compensation value, which can be obtained through calibration; The comprehensive target acceleration a cor Calculated by the following formula: a cor =max(a slope ,a mue ) Among them, a slope is the target acceleration converted from the road slope; a mue is the target acceleration converted from the road surface type.

4. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 3 is characterized in that: a mue The calculation method is as follows: and mue =mue*g; mue=c*mue1+(1-c)*mue2; Wherein, c is the weighting coefficient, 0≤c≤1; mue1 is the road adhesion coefficient obtained from the road type information; mue2 is the road adhesion coefficient obtained by estimation; F Road =F drv -F brk -F int ; F int =I*α / r whl ; Where, α is the rotational acceleration of the wheel; I is the moment of inertia of the wheel; F int is the wheel rotation inertia force; F brk is the wheel braking force; F drv is the wheel driving force; F Road is the road reaction force; a y is the lateral acceleration of the wheel; g is the acceleration due to gravity; mue long is the road adhesion coefficient in the longitudinal direction of the vehicle coordinate system; mue lat is the road adhesion coefficient in the lateral direction of the vehicle coordinate system.

5. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: The method for obtaining the feedback adjustment torque in step S4 is: S41, setting target parameter values ​​of vehicle operation parameters; S42, testing actual operating parameter values ​​of the vehicle under the feedforward basic torque drive; S43, calculating the difference between the target parameter value and the actual operating parameter value; S44, adjusting the feedforward basic torque through an algorithm according to the difference to obtain the feedback adjustment torque.

6. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1 or 5, characterized in that: The vehicle operating parameter for adjusting the feedforward basic torque in step S4 is one or more of the rotation speed of the driving wheel, the rotation acceleration of the driving wheel and the jerk of the driving wheel.

7. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: In step S4, when the automobile is a four-wheel drive vehicle, after obtaining the comprehensive torque, the comprehensive torque is distributed to the drive systems of the front axle and the rear axle according to the real-time dynamic loads of the front axle and the rear axle of the automobile for execution.

8. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: In step S5, whether the vehicle is in a stable driving state is determined by the rotational acceleration or jerk of the driving wheel; when the changes in the rotational acceleration or jerk of the driving wheel do not exceed the set value within the set time range, it is determined that the vehicle is in a stable driving state.

9. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: In step S6, in the stable acceleration mode, the comprehensive torque is gradually increased at a constant rate of change per unit time.

10. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 9, characterized in that: When the automobile is a four-wheel drive vehicle and the comprehensive torque is increased, the rate of change of the front axle per unit time is greater than the rate of change of the rear axle per unit time.

11. The control method for enhancing the driving ability of a vehicle on ice, snow or unpaved roads according to claim 1, characterized in that: In step S7, whether the driving wheel is in an unstable state is determined by the rotational acceleration or jerk of the driving wheel; when the rotational acceleration or jerk of the driving wheel is greater than a set value, it is determined that the driving wheel is in an unstable state.

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